Heat up a wok with the oil. Add the onion, lemongrass and Sriracha seasoning into the wok and fry for 4-5 minutes.
Add the prawns, stirring continuously until they are half-cooked, then add the hoisin sauce, fish sauce and water. Stir to combine well.
When the sauce starts to bubble and the prawns are cooked, add the spring onions into the wok, stir a few times, dish out and serve immediately with steamed rice.
